Project 2: Role of CACNA1C ? a shared risk factor in neuropsychiatric disorders ABSTRACT A major challenge in understanding human neuropsychiatric disorders has been the lack of viable tissues to analyze. Patient-derived induced pluripotent stem cells (iPSC) now offer the opportunity to examine the full complement of neural tissues and the prospect of identifying underlying disease mechanisms. Despite their promise, ?brain in a dish? models can be heterogeneous, masking similarities and subtle differences in disease-related phenotypes. Systematic development and validation of cell-based assays relevant to neuropsychiatric disease are therefore critically required. We are examining the effects of increased CACNA1C expression associated with the AA allele of rs1006737 -- the strongest and most replicated association with bipolar disorder (BP), and also implicated in schizophrenia (SZ) -- in neuronal differentiation and function.This work builds on published investigations in which we have demonstrated a role for CACNA1C in neurogenesis in animal models, and identified alterations in CACNA1C expression, calcium signaling, and neurotransmitter release in neurons differentiated from BP patients compared with those from healthy controls (C). Remarkably, lithium pre-treatment significantly reduced calcium transients and wave amplitude in BP neurons to control levels, providing a tractable model system to identify prognostic tests and examine the response of iPSC- derived neurons to pathway perturbagens and signaling networks suggested to be involved in BP. The overarching goal of the research is to identify predictive tests that distinguish common and divergent disease phenotypes and mechanisms in bipolar disorder and schizophrenia. The scientific hypothesis for this project is that dysregulation of calcium signaling produces subtle but widespread alterations in differentiation, plasticity and activity throughout the nervous system that influence susceptibility to bipolar disorder. Using neurons derived from carriers of the AA allele of rs1006737 and cells from control (GG allele) individuals, we will pursue three Specific Aims. Aim 1 will characterize the differentiation and behaviors of glutamatergic cortical neurons, including neurite outgrowth, synaptic and dendritic behavior, and mitochondrial status. Aim 2 will examine neuronal and network activity. Aim 3 will examine the differentiation of astrocytes and GABAergic neurons, and the effects of normalizing CACNA1C expression on neural differentiation in isogenic cell lines. These studies will directly test a long-standing theory regarding the role of altered calcium signaling in mood disorders and will produce a set of validated protocols comparing DISC1 mutant and BP iPSC, with high throughput analyses to identify novel mechanisms and signaling relevant to neuropsychiatric disease.